Meanwhile, former Massachusetts governor Mitt Romney solidified his frontrunner status and former Pennsylvania senator Rick Santorum came out of nowhere to claim the title of the latest in a long line of conservative alternatives to Romney.

Campaign buttons of Republican presidential hopeful Ron Paul at a rally at Jet Aviation January 6, 2012 in Nashua, New Hampshire. The New Hampshire primary is scheduled to be held January 10, 2012. AFP PHOTO/DON EMMERT

With so many changes in the field since the last debate, there’s lots to watch for in tonight’s proceedings. Below we highlight a few of the bigger storylines to keep an eye on. And don’t forget: We’ll be live-blogging the whole thing starting at 9-ish. Tune in!

* Mitt-mentum: Conventional wisdom is starting to congeal around the idea that Romney is the close-to-inevitable nominee. (See Jake Weisberg’s column for a smart argument making that point.)

If Romney glides through these twin debates — there will be another one at 9 a.m. tomorrow morning on NBC’s “Meet the Press” — it’s hard to see how anyone will come close to challenging him next Tuesday. (The latest Suffolk University tracking poll shows Romney with a 22-point lead over his nearest competitor.)

And if Romney sweeps to victory in New Hampshire, it’s getting tougher and tougher to see how he is derailed in his bid for the nomination given that a new CNN/Time poll released on Friday showed him with a wide edge over his rivals in South Carolina, which votes on Jan. 21.

Wins in the first three states now seems like a very real possibility for Romney unless someone can crack his un-crackable mien in these back-to-back debates. His opponents know that the “Romney as inevitable” storyline is starting to get legs and, as a result, will almost certainly go at him hard tonight and tomorrow.

* A Santorum/Gingrich alliance?: Think back about seven or eight debates ago to a time when neither Gingrich nor Santorum were even sniffing the top tier. In those set-to’s, the two former Members of Congress teamed up repeatedly to affirm one another and back up the other’s attacks on his/their rivals.

The question tonight is whether Santorum and Gingrich unite against their common political enemy — Romney — or whether they attack one another and, in so doing, make the former Massachusetts governor’s path to victory that much easier.

One course makes lots more political sense. That, of course, doesn’t mean either Gingrich or Santorum will follow it.

* Ron Paul, x factor: Lost in the avalanche of negative attacks against Gingrich in Iowa from Restore Our Future, a Romney-aligned super PAC, was how Paul went after his one-time colleague on TV too.

And now Paul is taking aim at Santorum with ads in South Carolina that cast the former Senator as a “corporate lobbyist and Washington politician” with “a record of betrayal”. Youch.

If Paul is willing to repeat those sorts of attacks in the debates tonight and tomorrow morning he will complicate Santorum’s attempt to keep the spotlight shining brightly on Romney’s past record. And if Paul winds up finishing second ahead of Santorum in New Hampshire, he may well be handing the nomination to Romney.

* Huntsman in search of a moment: Former Utah governor Jon Huntsman has spent all of his time (and money) in this presidential race in New Hampshire. And yet, he still doesn’t have much to show for it.

Why? Huntsman just hasn’t been able to find a moment to shine or distinguish himself from the rest of the field. The closest he has come was with an August tweet in which he affirmed his belief in evolution and climate change. That comment got lots of attention but it’s not a terribly effective message in a Republican presidential primary.

The twin debates tonight and tomorrow are Huntsman’s last chance to find a spark before New Hampshire primary on Tuesday. If he can’t make a moment, his time in the race is almost certainly over.

* WWRPD (What will Rick Perry do?): The Texas governor has already made clear that he is skipping the New Hampshire primary — and smartly so since most polls suggest he is in low single digits and could well lose to former Louisiana governor Buddy Roemer in the state on Tuesday.

The question is whether Perry’s decision to reverse course and stay in the race after finishing fifth in Iowa changes his approach at all. Is he more free-wheeling? More or less willing to swing at the other candidates? And, if so, which one(s)?

We remain somewhat baffled at why Perry decided to keep running after sending every signal that he would drop out. But, it’s possible he has something to prove to his supporters — and himself — over the next two weeks. The first day of the rest of Perry’s campaign starts tonight.